Transport System With Trucks Which are Driven by Means of Fuel Cells

ABSTRACT

A for transporting workpieces to be machined on or in a workpiece carrier between machining stations on or in rails, with movement elements, for example running wheels, wherein the movement elements are powered by a fuel cell.

CROSS REFERENCE TO RELATED APPLICATIONS

This case is the U.S. national phase of International Application No.PCT/EP2005/004748 filed May 2, 2005 which claims priority of GermanApplication No. 10 2004 026 562.3 filed May 27, 2004.

BACKGROUND OF THE INVENTION

The invention relates to a truck for transporting workpieces to bemachined on or in a workpiece carrier between machining stations on orin rails, with movement elements, for example running wheels, whereinthe movement elements are powered by a fuel cell.

PRIOR ART

A deck crane which is operated with a fuel cell as the drive source isknown from JP 2003276983 A. However, the present invention relates totransport systems which consist of a rail track on which a number oftrucks are arranged, which transport workpieces to a number of machiningstations arranged one behind another. The rail track forms a closedsystem which can guide the trucks by means of switches onto secondarytracks and from these back into the main track. Lifting arrangementswhich can guide the trucks onto rail tracks arranged at differentlevels, for example to bridge internal thoroughfares, are likewiseprovided. Such a system is described in DE 43 05 347 A, for example, anda truck is described in DE 195 06 670 A.

The trucks known thus far are either supplied with electrical energywith current conductors fastened to the rail tracks and slidingcontacts, and in some cases rolling contacts, or they contain powerstorage devices (batteries and/or super-capacitors), which have to berecharged at charging stations from time to time.

If workpieces which require a very clean environment (clean rooms) aretransported, sliding or rolling contacts are not possible for thepurpose of energy transmission because they contaminate the air.Supplying the truck drives by means of batteries carried in each truckhas the disadvantage of what is known as the memory effect, which occursowing to regular partial discharge and leads to only part of the energystored in the batteries actually being usable. The quantity of energywhich can be stored in super-capacitors is relatively small for theirvolume and their weight, which leads to the travel of a truck to thenext charging station having to be relatively short in order that theremaining energy is sufficient to manage this distance. The result ofthis is that many charging stations have to be provided in a completetransport system, with the corresponding cost consequences.

OBJECT

It is an object of the present invention to improve the drive on trucks.

SOLUTION FOR ACHIEVING THE OBJECT

The object is achieved by virtue of the fact that a fuel cell isassigned to the movement elements as the drive.

The disadvantages affecting the systems described above can beeliminated by providing the trucks with energy sources which neithercontaminate the air nor have the undesirable effect of partial energyuse. These conditions are satisfied by fuel cells. The functioning ofthe fuel cells concerned is not discussed in greater detail here. It isof importance only that both methanol and hydrogen can be used as theenergy carrier and that in one case water vapor and in small quantitiescarbon monoxide and carbon dioxide are produced as exhaust gas and inthe other case only water vapor is produced.

The trucks comprise a gas tank which is filled with one of the energycarriers mentioned at a filling station by automatic docking of a fillerpipe. In a further embodiment, the emptied cartridge is removedautomatically from the trucks at a filling station and a cartridgefilled with methanol or hydrogen is inserted. The time for filling-up orfor changing the cartridge of the individual truck is reached when theenergy quantity specified in the electronic tank monitoring system isreached by the continuously determined energy quantity measurement. Afurther advantage of the novel system can be seen in the fact that, atthe same volume, the energy quantity stored in the truck tank or in thetruck cartridge exceeds by a multiple that of the energy which can bestored in batteries or super-capacitors. This increases functionalautonomy considerably and, as a result of this, substantially fewercharging or filling stations are necessary.

The design of the rail tracks and of the other system components, suchas bends, switches, lifting arrangements, positioning devices etc.,which make up the complete transport system, remains unchanged inrelation to that described in the “prior art”.

1. A truck for transporting workpieces to be machined comprisingmovement elements and a fuel cell assigned to the movement elements asthe drive for the movement elements.
 2. Truck as claimed in claim 1,wherein the fuel cell is connected to a tank for an energy source. 3.Truck as claimed in claim 1, wherein the movement elements are wheels.